Refining copper



Patented Sept. 5, 1939 Herman 0. Kenny,

Lake Linden, Micln, assignor to Calumet & Hecla Consolidated Copper Company of Michigan, of Michigan Boston, Mass a corporation No Drawing. Application October 14, 1938, Serial No. 235,106

11 Claims.

The present invention relates to the refining of copper and more particularly to an improved process by which deoxidized copper of improved density and soundness may be produced.

-It is an object of the invention to provide an improved process for use in the refining and casting of copper. By my process, it is possible to produce an improved deoxidized copper. Further objects and advantages of the invention will in part be obvious and in part appear as the description proceeds.

This application is a continuation in part of my copending application Ser. No. 194,322, filed March '7, 1938.

In ordinary commercial tough pitch copper, the property of electrical conductivity is of importance. Impurities such as iron, silicon, aluminum, etc., if present in the metallic stateincopper, would impair the conductivity of the copper by going into solution therein. The presence of oxides of iron, silicon, aluminum, etc., however, does not impair the conductivity of the copper because these oxides are not soluble in the copper.

In the manufacture of copper, air is commonly blown through the molten copper, which has the effect of oxidizing the impurities such as iron, silicon, aluminum, etc. The oxidized impurities rise to the surface as slag and may be skimmed off. This oxidation treatment may also form up to about one per cent oxygen'as copper oxide. Later, poles of green wood are thrust into the molten copper. This operation, poling back, furnishes carbon and reduces the excess copper oxide again to metallic copper.

In order to insure that any impurities remaining in the copper shall be present'as oxides and thus shall not impair the electrical conductivity of the copper, the poling back is commonly carried only to the point of bringing the oxygen con- 7 tent of the molten copper bath down to about The presence of gases such as C0, C02, S02,

I H2O, etc., which are formed by reaction with this residual copper oxide in tough pitch copper, re-

duces the densityof the copper, so that whereas copper metal has a theoretical-density of 8.94, commercial tough pitch copper 'will commonly have a density in the neighborhood of 8.30 to 8.70. This decrease in density, however, is preferable to having a 'denser product. of impaired electrical conductivity in the .case of tough pitch copper.' oxide is of vital importance in controlling the pitch of cast cakes and in preventing shrinkage.

which is called powder, for example, may

Furthermore, the presence-of copper As distinguished from tough pitch copper, phosphorized copper is principally used for tubing, in which use the electrical conductivity of the copper is less important. It is therefore possible, with phosphorized copper, to get rid of substantially all of the oxygen from the molten copper bath, resulting in a denser product, for example, avdensity of the order of 8.85 or higher. This further reduction of the copper oxide content of the melt, with resultant increase in dens- 10 ity, is accomplished by poling back to below 0.04% copper oxide and then adding phosphorus in the form of phosphor-copper, an alloy which may, for example, contain phosphorus, to the melt, which results in the further removal of 15 oxygen, possibly as phosphorus oxide, copper. phosphate or both. A slight excess of phosphorus is conveniently used to insure the removal of substantially all of the oxygen, so that some residual phosphorus (for example 0.001 to 0.035%, depending on the customers demand) is likely to remain in the copper.

In accordance with my invention, the reaction of the phosphorus with the bath of molten copper is, at least in part, carried out in the presence of iron or aluminum. As a result, I am able to obtain a denser and improved phosphorized copper.

The iron or ious ways.

Merely stirring the copper melt which conaluminum may be supplied in vartains'oxygen and phosphorus with an iron rod for one or two minutes, for example, has been found highly advantageous. Or comminuted iron, in'the form of iron punchings. filings or be added to the melt, conveniently but not necessarily along with the phosphor-copper.

Molten copper baths commonly contain small quantities of sulfur. Or sulfur maybeintroduced with an alloying agent, such as arsenic, or may exist in the copper-phosphorus alloy. For reasons not fully understood, such sulfur appears to cause difliculty in reaching the desired density.

It is suggested that perhaps this may be due to a tendency for oxygen to form sulfur dioxide, a gas, instead of phosphorus oxide or copper phosphate, a solid which will slag off. The presence of iron, as above suggested, at the time of the reaction of the phosphorus with the copper melt, removes this difliculty and assists in the production ofv a denser and sounder: copper product.

whiie here againthe reaction or reactions involved are not fully understood, it is suggested that the iron may react with the sulfur toform a compound through the medium of which the sulfur as well as the iron may be slagged oil. The foregoing suggested reactions are to be taken merely as suggestions, however, and not in any limiting sense.

When adding comminuted iron to the copper bath it is well to give the bath a stir or twist, for example with a carbon rod. Or lesser amounts of comminuted iron may be used if the bath is stirred for a time with an iron rod. Thus when stirring a molten copper bath for 15 seconds with an iron rod, roughly 10 grams of iron may be dissolved from the rod, so that the amount of iron added to the bath in some other form may be correspondingly reduced.

The amount of iron to be added for best results will vary with the percentage of sulfur in the copper melt. The addition of increasing amounts of iron will in general result in an increase in density of the final product up to a certain point, at which addition of further amounts of iron willresult in decreasing the density of the product. Due to the fact that the ratio of impurities difiers in every bath of molten copper, it is not practical to set any specific limits in advance on the amount of iron to be added. For example, with one batch of copper, it was found that whereas additions of iron up to 34 grams per ladle (a ladle containing approximately 350 pounds of molten copper) resulted in a progressive increase in density, addition of iron in excess of 34 grams per ladle caused a rather sharp drop in density of the product. With other ladles of higher sulfur content, it was found that the addition of iron up to approximately 50 grams and more per ladle resulted in progressive increase in density. Sulfur anlyses on refined copper are none tooaccurate at best and they take considerable time. The most advantageous amount of iron for a given ladle of molten copper is, however, readily determined in practice. As an example, excellent results have been obtained using about 30 grams of comminuted iron per ladle (approximately 350 pounds) of molten copper.

It is advantageous to use the minimum amount of iron which will give the desired density, in order to avoid the presence of a large excess of iron in the product. Ordinarily, not over 0.10% by weight of iron should be added to the bath. Excellent results have been obtained-with smaller quantities, for example of the order of 0.06%, 0.05%, or less.

The estimated amount of iron may be added to .each ladle and the quantity adjusted after the product has been examined or tested.

As previously indicated, aluminum may also be used in my process, for the production of my improved deoxidized copper. lar to those outlined above also apply, in general, to the use of aluminum. For example, very good results have been obtained by the addition of to 40 grams of aluminum turnings per ladle of molten copper, stirring for thirty seconds with a carbon rod. Good results are usually obtained with amounts of aluminum not exceeding 0.04% by weight, although amounts up to 0.10% may be used.

The final product produced by my process may be a copper of improved soundness and having a density of 8.85 and higher. I have prepared copper of a density of 8.90 substantially free of sulfur.

Having thus described my invention, I claim:

1. In a process for refining copper, the step Considerations simiwhich comprises reacting phosphorus with molten copper in the presence of an added substance selected from the group consisting of iron and aluminum, said iron or aluminum being added in amount suificient to densify the metal and not exceeding 0.1% of the weight of the copper, whereby the density and soundness of the resulting copper product are increased.

2. In a process for refining copper, the step which comprises reacting phosphorus with molten copper containing oxygen, in the presence of added metallic iron, said iron being present in amount not exceeding 0.1% of the weight of the copper and in an amount sufiicient to densify the copper, whereby the density and soundness of the resulting copper product are increased. V

3. In a process for refining copper, the step which comprises reacting phosphorus with moiten copper containing oxygen and sulfur, in the presence of an amount of added iron not exceeding 0.1% of the weight of the copper and sufiicient to densify the resulting copper product.

4. In a process for refining copper, the step which comprises adding phosphorus and aluminum to molten copper which contains oxygen and sulfur, said aluminum being added in amount not exceeding 0.1% of the weight of the copper and sufiicient to densify the copper, whereby the density and soundness of the resulting copper product are increased.

5. In a process for refining copper, the step which comprises adding phosphorus and a metal selected from the group consisting of iron and aluminum to a molten copper bath containing oxygen, said iron or aluminum being added in amount suflicient to densify the copper and not exceeding 0.05% by weight of the copper bath.

6. In a process for refining copper, the step which comprises adding phosphorus and comminuted iron to a molten copper bath containing oxygen and sulfur, said iron being added in amount not exceeding 0.1% of the weight of the copper and in an amou t sufiicient to densify the copper.

7. In a process for refining copper, the steps which comprise adding phosphorus and iron to molten copper which contains oxygen and agitating said molten copper in the presence of said iron, said iron being added in amount not exceeding 0.05% of the weight of the copper and in an amount sufiicient to densify the resulting copper product.

8. In a process for refining copper, the steps which comprise adding phosphorus and aluminum to molten copper which contains oxygen, the aluminum being added in amount not exceeding 0.04% of the weight of the copper and inan amount sufiicient to densify the copper, and agitating said molten copper in the presence of said aluminum.

9. A process for improving the density and soundness of castings of phosphorized copper, which process comprises preparing 'a molten copper bath containing oxygen, phosphorus and not over 0.1% by weight of a substance selected from the group consisting of iron and aluminum, said iron or aluminum being added in amount sufiicient to increase the density hf the copper product, permitting chemical reaction between in gredients of said bath, removing slag from said bath and casting the molten copper.

10. In a process for the manufacture of phosphorized copper, the step which comprises adding a substance selected from the group consisting of iron and aluminum, in regulated amounts not exceeding 0.1% 'of the weight of the copper, to control the density and soundness of-the phosphorized copper.

11. As an article of manufacture, phosphorus deoxidized copper containing an element selected from the group consisting of iron and aluminum,

added in amount suflicient to density the copper product but not exceeding 0.1% of the weight of the copper, said copper product being substantially free from sulfur and having a. density in excess of 8.85.

HERMAN C. KENNY. 

